Switching between delivery methods in an IPTV communication network

ABSTRACT

A method and apparatus for switching from a first IPTV channel arranged to be delivered to a plurality of nodes, such as a broadcast or a unicast, to a second unicast IPTV channel. The first IPTV channel is received at an IPTV receiving node, such as a User Equipment. If it is determined that the first IPTV channel is no longer available, then an IPTV content provider capable of providing the same IPTV channel in a unicast as the first IPTV channel is identified. A message is then sent to an IPTV AS, the message including an instruction to switch to a unicast IPTV channel and an address for the identified IPTV content provider node. The IPTV receiving node then receives the IPTV channel unicast.

CLAIM OF PRIORITY

This application is a continuation application of U.S. patentapplication Ser. No. 12/993,324, filed Nov. 18, 2010, now U.S. Pat. No.9,621,364 issued Apr. 11, 2017, which is a 371 of InternationalApplication No. PCT/EP2008/056110, filed May 19, 2008. The disclosuresof these documents are hereby incorporated herein by reference.

TECHNICAL FIELD

The invention relates to the field of IPTV communication networks, andin particular to switching between broadcast/multicast and unicastdelivery of IPTV.

BACKGROUND

TV services broadcast over an IP network are referred to as IPTV. IPTVis typically broadcast using a broadband access network, in whichchannels are transmitted over a broadband network from a super head-enddown to an end-user's set top box (STB). An example of an IPTV serviceis Broadcast TV, in which the most common IPTV channels, as well asadditional channels with low penetration, are transmitted over abroadband network from a super head-end down to an end-user's set topbox (STB). In order to minimize the bandwidth required for thesetransmissions it is desirable to use multicast techniques through thenetwork.

Similarly, in mobile networks it is desirable to use broadcast/multicastdelivery of Mobile TV (MTV). Multimedia Broadcast Multicast Service(MBMS) and Digital Video Broadcasting-Handheld (DVB-H) are examples ofMTV broadcast technologies. A mobile telephone having an MTV client canbe thought of as an equivalent to a STB in MTV implementations thatreceive content from a super head-end. The term “Linear TV” is used torefer to “live” ITV, which is typically delivered by broadcasting.

The same set of channels delivered over broadcast bearers may in mobilenetworks also be offered over dedicated unicast bearers. In thisscenario, each user is allocated a dedicated channel. This is incontrast to a common bearer used in broadcast delivery over, forexample, MBMS. Even though allocating a dedicated channel is lessefficient from a transmission point of view, it is a pragmatic solutionfor many mobile networks in which broadcast delivery is not available inall geographical areas (cells). A network operator may choose to onlyimplement MBMS in areas with high subscriber density. In some areas,MBMS has not yet been implemented, and in other areas, MBMS may never beimplemented. This creates a need for delivering Linear TV over bothbroadcast and unicast bearers.

Furthermore, a user may start viewing an IPTV channel over an MBMSbroadcast bearer, and subsequently move into an area where MBMS is notsupported. In this scenario, it is necessary to switch from a broadcastdelivery of Linear TV to a unicast delivery. Such a switch should be assmooth as possible and cause the least disruption to the user's viewing.

Currently there is no mechanism for switching betweenbroadcast/multicast and unicast delivery of Linear TV.

SUMMARY

The inventors have realised that no mechanism exists for switchingbetween delivery methods in an IPTV network, and in particular toswitching from a broadcast or multicast IPTV channel to a unicast IPTVchannel when the broadcast/multicast IPTV channel becomes unavailable.This may occur, for example, when an MTV user moves from an area inwhich broadcast/multicast IPTV is supported to an area in whichbroadcast IPTV is not supported. According to a first aspect of theinvention, there is provided a method of switching from a first IPTVchannel arranged to be delivered to a plurality of nodes to a secondunicast IPTV channel. The method comprises receiving the first IPtelevision channel at an IPTV receiving node, such as a User Equipment.If it is determined that the first IPTV channel is no longer available,then an IP television content provider capable of providing the sameIPTV channel in a unicast as the first IPTV channel is identified. Amessage is then sent to an IPTV Application Server (AS), and the messageincludes an instruction to switch to a unicast IPTV channel and anaddress for the identified IPTV content provider node. The IPTVreceiving node then receives the IPTV channel unicast.

The method is optionally suitable for use where the first IPTV channelis delivered by either a broadcast or a multicast. In most cases theIPTV receiving node is capable of receiving a plurality of channels, andso the instruction to switch to a unicast IP television channeloptionally applies to all IP television channels provided to the IPTVreceiving node.

As an option, the IPTV channels are provided in a Mobile IP televisionnetwork. In this case, the determination that the first IPTV channel isno longer available may made as a result of the IPTV receiving nodemoving to an area in which the first IPTV channel is not provided. Thisis because some networks do not provide broadcast or multicast IPTV atall, but only unicast IPTV.

As an option, the IPTV content provider capable of providing the sameIPTV channel in a unicast is identified from data contained in anElectronic Programme/Service Guide (ESG/EPG) stored at the IPTVreceiving node.

The method is particularly suitable for use where the IPTV AS is locatedin an IMS network, in which case the message is a SIP Invite message.Note that SIP signalling may also be used in networks other than IMSnetworks. Where SIP signalling is used, the instruction to switch to aunicast IP television channel is optionally contained in a ServiceAction Data parameter in the SIP Invite message.

The user may subsequently move into an area where a broadcast ormulticast is once again available. If it is determined that the first IPtelevision channel is available, then the method optionally comprisesidentifying an IP television content provider capable of providing thefirst IP television channel, and sending a further message to the IPtelevision Application Server. The further message includes aninstruction to switch to the first IP television channel and an addressfor the identified broadcast IP television content provider. The IPTVreceiving node once again receives the first IP television channel.

According to a second aspect of the invention, there is provided areceiving node for receiving an IP television channel. A first receiveris provided for receiving a first IPTV channel that is arranged to bedelivered to a plurality of nodes. Examples of such an IPTV channel aremulticast and broadcast channels. A first processor is arranged todetermine that the first IPTV channel is no longer available, and asecond processor is used for identifying an IPTV content providercapable of providing the same IP television channel in a unicast as thefirst IPTV channel. A transmitter is provided for sending a message toan IPTV AS. The message includes an instruction to switch to a unicastIP television channel and an address for the identified IPTV contentprovider. A second receiver is also provided for receiving the unicastIPTV channel.

As an option, the receiving node is a mobile device such as UserEquipment in an IMS network.

The receiving node optionally comprises a memory for storing anElectronic Program/Service guide, the Electronic Program/Service guidecomprising information about broadcast and unicast IP televisionchannels. This information is used to identify the IPTV content providercapable of providing the same IP television channel in a unicast as thefirst IPTV channel.

According to a third aspect of the invention, there is provided an IPTVAS. The IPTV AS has a first receiver for receiving from an IPTVreceiving node a SIP Invite message, the SIP invite message including aninstruction to switch to a unicast IP television channel and an addressfor an IP television content provider node, and a first transmitter forsending to the identified content provider a message requesting that theunicast IP television channel is provided to the IP television receivingnode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically in a block diagram the signallingrequired to receive a MTV broadcast at a MTV client;

FIG. 2 illustrates schematically in a block diagram the signallingrequired to receive a MTV unicast at a MTV client;

FIG. 3 illustrates schematically in a block diagram the signallingrequired for fast channel switching at an MTV client for a MTV unicast;

FIG. 4 illustrates schematically in a block diagram the signallingrequired for fast channel switching at an MTV client for an IPMultimedia Subsystem delivered MTV unicast;

FIG. 5 illustrates schematically in a block diagram the signallingrequired for establishing a broadcast IPTV session;

FIG. 6 illustrates schematically in a block diagram further signallingrequired to change from a broadcast to a unicast delivery according toan embodiment of the invention;

FIG. 7 is a flow diagram showing the steps of an embodiment of theinvention;

FIG. 8 illustrates schematically in a block diagram a MTV client nodeaccording to an embodiment of the invention; and

FIG. 9 illustrates schematically in a block diagram a MTV ApplicationServer according to an embodiment of the invention.

DETAILED DESCRIPTION

The following description sets forth specific details, such asparticular embodiments, procedures, techniques, etc. for purposes ofexplanation and not limitation. In some instances, detailed descriptionsof well known methods, interfaces, circuits, and devices are omitted soas not obscure the description with unnecessary detail. Moreover,individual blocks are shown in some of the drawings. It will beappreciated that the functions of those blocks may be implemented usingindividual hardware circuits, using software programs and data, inconjunction with a suitably programmed digital microprocessor or generalpurpose computer, using application specific integrated circuitry,and/or using one or more digital signal processors.

Referring now to FIG. 1, an existing procedure for broadcast delivery ofLinear TV, which could be IPTV, or more specifically MTV, is shown. Theexample illustrates the signalling between nodes in an IP MultimediaSubsystem (IMS) network, but similar signalling could apply in othertypes of network. For example, whilst the following example refers toSIP signalling, other types of signalling such a HTTP may be used. Thefollowing numbering corresponds to the numbering in FIG. 1.

S1. An MTV Client 1 sends an Invite requesting access to broadcastLinear TV content. The MTV service is identified in the Invite using anIMS Communication Service Identifier (ICSI) for the IPTV communicationservice, and a Public Service Identifier (PSI) for the MTV ServiceProvider of broadcast TV. The Invite is sent to a Proxy-Call SessionControl Function (P-CSCF) 2.

S2. The P-CSCF 2 forwards the Invite to a Serving-Call Session ControlFunction (S-CSCF) 3.

S3. The S-CSCF 3 uses the ICSI to identify the MTV service and sends theInvite to a MTV

Application Server (MTV-AS) 4. In this example, the MTV service providerand the IMS operator are the same entity, although they may be separateentities. This allows user specific originating triggers (originatingS-CSCF 3) to invoke the MTV AS 4.

S4-S5. The MTV-AS 4 is responsible for content key handling for IPTV.Before users are allowed to use the IPTV over IMS solution, they areauthenticated to access IMS services using inherent IMS securityprovided by e.g. IMS AKA. For traffic (signalling and payload) that isnot transferred over IMS, users are authenticated with GBA procedures.HTTP for EPG (Electronic Program Guide) retrieval is an example of suchsignalling. A Bootstrapping Server Function (BSF) in the GBAarchitecture performs the authentication of non-IMS traffic, and asubscriber specific key named Ks_NAF is generated as part of theprocedure.

S6. The MTV-AS 4 is responsible for delivering the content keys to aBroadcast Multicast Service Centre (BM-SC) 6, which is responsible fordelivering broadcast content to the MTV client 1.

S8-12. The MBMS Group Key (MSK) is delivered to the MTV Client 1, afterwhich the MTV client 1 can begin content access for MBMS deliveredcontent from the BM-SC 6. Ks_NAF, which was generated during the GBAbootstrapping procedure, may be used to encrypt the MSK when it is sentto the receiving node at which the MN client 1 is located. An example ofsuch a receiving node is User Equipment (UE). Other means to deliver theMSK to the UE could also be used. Decoding of the traffic channel (MTCH)is started by the UE. The MTK (content keys) that are sent over the MTCHare decrypted with the MSK, to allow the content to be decrypted. TheMTK is used to decode Secure Real-time Transport Protocol (SRTP) contentbefore it can be rendered for the user to view. Note that secure payloadformats other than SRTP could also be used.

Referring now to FIG. 2, an existing procedure for session establishmentfor unicast delivery of Linear TV is shown. The example illustrates thesignalling between nodes in an IP Multimedia Subsystem (IMS) network,but similar signalling could apply in other types of network.

In steps S13 to S32 of FIG. 2, the MTV client 1 establishes asession/connection for media delivery to a Content Server 7 for LinearTV by sending an Invite with a PSI for unicast delivery of Linear TV,and optionally identification of the TV service (ICSI). The MN clientobtains the necessary URIs for Linear TV channels using a previouslyexecuted Electronic Programme Guide (EPG) retrieval procedure. It ispossible for the MTV client 1 to probe the Content Server 7 to ascertainwhether if it supports fast channel switching.

Note that all channels available in the Linear TV offering from theService Providers are delivered over the same unicast bearer. Onechannel is delivered at any one time, and if a user changes from channelto another, the content server 7 changes the programme currentlydelivered to the MTV client 1.

In the broadcast case described above, all of the channels aretransmitted on the broadcast channel from the BM-SC 6, and a channelswitch can be performed locally at the UE in which the MTV client 1 islocated. However, for a unicast, channel switching must be performed atthe media source (the content server 7), as illustrated in FIG. 3.

Fast channel switching was introduced in 3GPP PSS (Packet StreamingService) to enable a channel switch at the media source, withoutrequiring the establishment of a new RTSP session for the new channel.In step S33, the client 1 is receiving audio and video data for channel1 from a Content Server 7. The user then decides to change channel, sothe client 1 is instructed to send in step S34 a “Play Command” thatcontains a channel indication (c2 in this example) to the Content Server7. In step S35, the Content Server replies with a 200 OK message, and instep S36 the Content Server 7 provides the client 1 with audio and videofor channel 2.

A similar capability is provided in the IMS delivered MTV solution, and,as with the PSS solution illustrated in FIG. 3, it requires that themedia source performs the switch between the channels. FIG. 4illustrates Fast Channel Switching (FCS) in an IMS delivered Mobile TVunicast. In step S37, a Content Server 7 provides the MN client 1 withmedia for a first channel. In step S38, the user initiates a channelswitch, and in step S39 the MTV client 1 sends to the Content Server 7 aRTSP Play message including a “Switch Stream” header that identifies therequired new channel. The Switch-Stream header contains informationabout the old and new streams expressed as RTSP URLs. In step S40, theContent Server 7 replies with a 200 OK message, and in step S41, theContent Server 7 starts to send media for the new channel to the MTVclient 1.

Turning now to FIG. 5, Trick Play is defined in Tispan (IPTV, MTV) andgives the user the ability to control an IPTV broadcast with actionssuch as Play, Pause, Stop, in a similar manner to the way in which a VCRor DVD player can be used to control video playback. Trick Playfunctions should only apply to that user and not all users, and so wheremedia is delivered in a broadcast and a user initiates Trick Play, themedia must be provided in a unicast for that user. This is described inthe Tispan IPTV specification and will serve as a basis for the MobileTV standardization in 3GPP “IMS initiated and controlled MBMS and PSS”.

FIG. 5 shows the change from Linear broadcast TV to Trick Play controlfor one specific channel.

S42. The MTV Client 1 establishes a session for reception of BroadcastLinear TV as previously described.

S43-48. When a user has stayed with a particular broadcast channel for acertain time, the MTV AS 4 is updated with information about thecurrently viewed channel. The update is sent using SIP signalling viathe P-CSCF 2 and the S-CSCF 3. A SIP Info containing a Service ActionData information element is sent, and the information can be used forstatistical purposes. It may include BC Service Id, Programme Id, etc

S49. The user then requests Trick Play. MTV Client 1 sends a Re-inviteusing the established SIP dialogue to the P-CSCF 2. The Invite containsa Service Action Data information element with an indication to “switchto Trick Play”. If SIP Info with the required Service Action Data hasnot previously been sent with information about the currently viewedchannel, then channel information is included in the Service ActionData. The Invite includes SDP information for audio, video and TCP (thelatter is required because RTSP commands will be sent over TCP). TheRe-invite message is sent to the MTV AS 4 via the S-CSCF 3, and the MTVAS 4 negotiates the audio and video RTSP set-up with the Media Server(MCF/MDF in Tispan) 8. The MTV AS 4 may use SIP or RTSP to establish asession with the Media Server/n-PVR. The MTV Client can however directlysend RTSP commands to control a Personal Video Recorder (PVR) via theestablished TCP connection without mediation and involvement by the MTVAS 4. An example of such a command is to Pause the linear TV unicast.

The above described signalling is modified according to the invention toallow for switching between broadcast and unicast delivery of Linear TV.

Information about available TV channels and how they are delivered(broadcast or unicast) is found in the EPG/ESG and this informationinstructs the MTV client 1 if broadcast or unicast delivery is used fora certain channel. When Linear TV is delivered by both broadcast andunicast delivery, addresses and other information necessary for unicastand broadcast delivery are included together with an indication of theoperator's preferred choice (e.g. always use MBMS if available in thecurrent area).

When requesting Trick Play, unicast is requested for one channel only.However, if it is detected that broadcast delivery of Linear TV is nolonger available, for example because a mobile user moves to an areawhere MBMS broadcast is not supported, then it will be necessary to moveto unicast delivery of all channels.

When it is required to switch from broadcast to unicast delivery ofLinear TV, the initial signalling is the same as that shown in FIG. 5,with the exception that Trick Play is not requested. The followingsignalling, with numbering corresponding to that shown in FIG. 6,

S50. The MTV client 1 sends a Re-invite using the established SIPdialogue to the P-CSCF 2. The Re-Invite contains a Service Action Datainformation Element with an indication of “Switch to Unicast Delivery”defined as a new value for the Service Action Data information element.This indication informs the MTV AS 4 which content server (in this case,the MDF/Content 8) should be used, and the content server must provideunicast Linear TV. The request for unicast delivery applies to allchannels provided to the MTV client.

S51-52. The SIP Re-invite is sent to the MTV AS 4 via the S-CSCF 3.

S53-56. The MTV AS 4 negotiates the audio and video RTSP set-up with theMedia Server (MCF/MDF) 8. The RTSP Play command contains the channelthat the user wishes to watch, i.e. typically the channel the user waswatching via broadcast delivery before the switch to unicast deliverybecame necessary.

S57-61. A SIP 200 OK is returned to the MTV Client 1 in response to theRe-Invite message sent in S50.

S62-65. IMS Policy and Charging Control (PCC) functionality is used toassign an appropriate bearer (defined by QoS requirements) for theunicast IPTV delivery. These steps show a network controlled bearerestablishment/PDP context, but a UE controlled bearer establishmentcould also be used.

S66-67. The MTV client 1 initiates the RTSP stream for the selectedunicast channel to complete the switch to unicast channel delivery.

Of course, if a user then moves back into an area that does supportdelivery of Linear TV by broadcast, the same signalling as describedabove can be used to switch back from unicast to broadcast, simply bysending a re-invite similar to that in step S50, but with the ServiceAction Data Element having in indication of “Switch to Broadcastdelivery”.

Referring now to FIG. 7, an exemplary embodiment of the invention isdescribed below. The following numbering corresponds to the steps shownin FIG. 7.

S68. An MTV client 1 receives a broadcast IPTV channel.

S69. The MTV client 1 moves to a geographical area in which broadcastIPTV is not available, and a determination that broadcast IPTV is notavailable is made.

S70. The MTV client 1 determines a unicast channel providing the samemedia as the broadcast IPTV channel from data contained in the ESG orEPG.

S50. A SIP Re-invite is sent to the MTV-AS 4 that includes aninstruction to switch to the unicast IP television, and an address forthe identified IP television content provider node.

S71. The MTV client now receives the unicast IPTV channel rather thanthe broadcast IPTV channel.

S72. In the event that the MTV client 1 subsequently moves to an areawhere broadcast IPTV is available, a determination is made thatbroadcast IPTV is available.

S73. The MTV client 1 determines a broadcast channel providing the samemedia as the unicast IPTV channel from data contained in the ESG or EPG.

S74. A SIP Re-invite is sent to the MTV-AS 4 that includes aninstruction to switch to broadcast IP television, and an address for theidentified broadcast IP television content provider node. The MTV client1 in the UE will typically tune in to the TV channel watched by the userbefore the switch from unicast to broadcast.

S75. The MTV client now receives the broadcast IPTV channel rather thanthe unicast IPTV channel.

Turning now to FIG. 8, there is illustrated a MTV client node 1according to an embodiment of the invention. The MTV client node 1 has afirst receiver 9 for a broadcast IP television channel, and a firstprocessor 10 for determining that the broadcast IPTV channel is nolonger available. A second processor 12, which is typically the sameprocessor as the first processor, is provided for identifying an IPtelevision content provider capable of providing the same IP televisionchannel in a unicast as the broadcast IP television channel. Thisdetermination is made from ESG/EPG data stored in a memory 12. Atransmitter 13 is provided for sending a SIP Invite message to a MTV-AS4, the SIP Invite message including an instruction to switch to aunicast IP television channel and an address for the identified IPtelevision content provider. A second receiver 14 is also provided forreceiving the unicast IP television channel.

FIG. 9 herein illustrates an MTV AS 4 according to an embodiment of theinvention. The MTV AS 4 has a receiver 15 for receiving from the MTVclient 1 a SIP Invite message, the SIP Invite message including aninstruction to switch to a unicast IP television channel and an addressfor an IP television content provider. A transmitter 16 is also providedfor sending to the identified content provider a message requesting thatthe unicast IP television channel is provided to the MTV client 1. Aprocessor 17 is also provided for managing signalling.

The invention provides a smooth and fast switch between Linear TVdelivered over broadcast and unicast bearers. A new value is introducedinto signalling procedures that is used for requesting a change of thedelivery method from broadcast to unicast.

It will be appreciated by the person of skill in the art that variousmodifications may be made to the above-described embodiments withoutdeparting from the scope of the present invention. For example, whilstthe above description discusses the invention in the context of a MobileTV network, and a loss of broadcast IPTV because a user roams to an areain which broadcast IPTV is not available, it will be appreciated thatthe invention also applies to fixed access IPTV networks where an IPTVbroadcast becomes unavailable. This may be, for example, due to afailure of the broadcast IPTV server.

The following abbreviations have been used in this specification:

-   CoD: Content on Demand-   EPG: Electronic Programme Guide-   ESG: Electronic Service Guide-   DVB-H Digital Video Broadcasting-Handheld-   GBA Generic Bootstrapping Architecture-   GAA Generic Authentication Architecture-   HTTP: Hypertext Transfer Protocol-   Linear TV “Live TV”-   MCF Media Control Function-   MDF Media Delivery Function-   MSK MBMS Session Key-   MTK MBMS Traffic Key-   MTV: Mobile TV-   MBMS Multimedia Broadcast Multicast Service (MBMS)-   nPVR: Network based Personal Video Recorder-   STB: Set Top Box-   SRTP Secure Real-time Transport Protocol-   Head-end The central part of an IPTV distribution system responsible    for Programme Acquisition, content encoding, access right    management, etc-   Trick Play The ability to control the Linear TV broadcast with    actions similar to the actions possible to perform on a    VCR/DVD-Player such as Play, Pause, Stop, etc.-   URI: Uniform Resource Identifier-   XCAP: XML Configuration Access Protocol.-   XDMS: XML Data Management Server

The invention claimed is:
 1. A method of switching from a first InternetProtocol (IP) television channel arranged to be delivered to a pluralityof nodes, to a unicast second IP television channel, the methodcomprising: at an IP television receiving node, receiving the first IPtelevision channel; determining that the first IP television channel isno longer available; identifying an IP television content providercapable of providing the same IP television channel in a unicast as thefirst IP television channel; sending a message to a network node, themessage including an instruction to switch to the unicast second IPtelevision channel and informing the network node which IP televisioncontent provider to use; and receiving the unicast second IP televisionchannel.
 2. The method according to claim 1, wherein the first IPtelevision channel is arranged to be delivered using one of a broadcastand a multicast delivery method.
 3. The method according to claim 1,wherein the instruction to switch to the unicast second IP televisionchannel applies to all IP television channels provided to the IPtelevision receiving node.
 4. The method according to claim 1, whereinthe IP television channels are provided in a Mobile IP televisionnetwork.
 5. The method according to claim 1, further comprisingdetermining that the first channel is no longer available.
 6. The methodaccording to claim 1, wherein the network node is an IP televisionApplication Server located in an IP Multimedia Subsystem network.
 7. Themethod according to claim 1, wherein the message is a Session InitiationProtocol Invite message.
 8. The method according to claim 7, wherein theinstruction to switch to the unicast second IP television channel iscontained in a Service Action Data parameter in the SIP Invite message.9. The method according to claim 1, further comprising: determining thatthe first IP television channel is available; sending a further messageto the network node, the further message including an instruction toswitch from the unicast second IP television channel to the first IPtelevision channel; and receiving the first IP television channel.
 10. Areceiving node for receiving an Internet Protocol (IP) televisionchannel, the receiving node comprising: processing circuitry and amemory, the memory containing instructions executable by the processingcircuitry whereby the receiving node is configured to: receive a firstmulticast IP television channel that is arranged to be delivered to aplurality of nodes: determine that the first IP television channel is nolonger available; identify an IP television content provider capable ofproviding the same IP television channel in a unicast as the first IPtelevision channel; send a message to a network node, the messageincluding an instruction to switch to the unicast second IP televisionchannel and informing the network node which IP television contentprovider to use; and receive the unicast second IP television channel.11. The receiving node according to claim 10, wherein the receiving nodeis a mobile device.
 12. The receiving node according to claim 10,wherein memory is configured to store an Electronic Program/Serviceguide, the Electronic Program/Service guide comprising information aboutbroadcast and unicast IP television channels.
 13. A network nodecomprising: processing circuitry and a memory, the memory containinginstructions executable by the processing circuitry whereby the node isconfigured to: receive from an Internet Protocol (IP) televisionreceiving node a message including an instruction to switch during anongoing session to a unicast IP television channel and information aboutwhich IP television content provider that provides the unicast IPtelevision channel; and send to the identified IP television contentprovider a message requesting that the unicast IP television channel isprovided to the IP television receiving node.
 14. The network nodeaccording to claim 13, wherein the network node is an IP televisionApplication Server.
 15. A method of enabling switching for an InternetProtocol (IP) television receiving node from a first IP televisionchannel arranged to be delivered to a plurality of nodes, to a unicastsecond IP television channel, the method comprising: receiving from theIP television receiving node a message including an instruction toswitch during an ongoing session to a unicast IP television channel andinformation about which IP television content provider node thatprovides the unicast IP television channel; and sending to theidentified IP television content provider a message requesting that theunicast IP television channel is provided to the IP television receivingnode.